Japan’s finance ministry has admitted doctoring documents in a widening scandal linked to Prime Minister Shinzo Abe’s wife which has rattled his government and caused a slide in support.

Mr Abe quickly apologised on behalf of ministry officials but did not mention his wife Akie Abe or her suspected role in the scandal.

He said: “People are looking critically at the developments, and I take it seriously.”

The PM also promised to pursue a thorough investigation into the issue.

The altered documents relate to the 2016 sale of state land to school operator Moritomo Gakuen in Osaka at one-seventh of the appraised value, with the alleged involvement of Mrs Abe, who supported the school’s ultra-nationalistic education policy.

Mr Abe has promised a full investigation (AP)

An investigation by the ministry showed there had been contacts from Mrs Abe and several conservative MPs over the school plan, but it was not clear whether they had violated any law.

The scandal, which surfaced a year ago, has smouldered despite a major election victory by Mr Abe in July as opposition MPs continued to scrutinise the case. It erupted again in recent weeks after a major newspaper reported that it found evidence the ministry had altered records after the scandal broke.

Finance minister Taro Aso said the investigation found 14 altered documents. The changes were made from February to April last year at the instruction of the Financial Bureau, the ministry department in charge of state property transactions said.

Mr Aso said the documents were falsified to match explanations that an official in charge of the land deal, Nobuhisa Sagawa, provided to parliament in response to opposition MPs’ questions.

Mr Sagawa was later promoted to National Tax Agency chief in what critics alleged was a reward for stonewalling the questioning. He resigned last Friday to take responsibility for his replies, and another official linked to the scandal reportedly killed himself. Mr Sagawa also acknowledged destroying documents.

Mr Aso denied there had been any political pressure, but declined to disclose where the instructions came from and who was responsible.

The prime minister said Mr Aso will not step down.

In a parliamentary hearing, finance ministry officials confirmed that a reference to Akie Abe having recommended the land deal was deleted from a document after the scandal surfaced.

Yasunori Kagoike, then head of Moritomo Gakuen, purchased the land to build an elementary school where Mr Abe’s wife briefly served as honorary principal. The Abes are known to have supported the school’s nationalistic philosophy of education.

A phrase calling the land deal “exceptional”, as well as the names of several other influential MPs who were implicated but have denied involvement, were also deleted, the ministry said.

Opposition MPs allege political pressure was involved in the land sale, but Mr Abe has repeatedly denied any wrongdoing.

The conservative Yomiuri newspaper and public broadcaster NHK both reported declines in support ratings for Mr Abe’s cabinet in new polls.